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Performance Issues with Unity Catalog

Mystagon
New Contributor II
Hey I need some help /  suggestions troubleshooting this, I have two DataBricks Workspaces Common and Lakehouse.
 
There difference between them is:
 
Major Differences:
- Lakehouse is using Unity Catalog
- Lakehouse is using External Locations whereas credentials are set using service principal for Common.
- Listing directories in common is at least 4-8 times faster than Lakehouse environment.
- Lakehouse is in VNET and is accessed using company VPN.
 
Configuration:
- Both DLT pipelines are configured the same except for catalog location and since common isn't UC it is saved to a dbfs location.
- Both DLT pipelines are reading from the same storage container. Other than that nothing else is different.
 
DLT Comparisons:
 
- Common (17m 21s) + 5 minutes because cluster is already running.
- 0m - Task Starts (Cluster already running) Initialising
- 0m 30s Setting Up Tables (7m 30s)
- 8m Graph Initialised and tables are being populated (9m 30s)
- 17m 30s All tables complete 
 
- Lakehouse (1h 17m 23s)
- 0m - Task Starts (Spinning up Cluster)
- 4m 30s Initialising (15m 20s)
- 19m 50s Setting Up tables (47m)
- 1h 6m 50 Graph Initialised and tables are being populated (11m)
- 1h 17 23s All tables complete 
 
I am assuming there is bottleneck somewhere but having a hard time troubleshooting it. I think it could be one of the following Unity Catalog overhead or VPN performance between Databricks and Storage Container.
1 REPLY 1

Lakshay
Esteemed Contributor
Esteemed Contributor

This needs a detailed analysis to understand the root cause. But a good point to start is to compare the Spark Ui for both runs and identify which part of execution is taking time. And then we need to look at the logs.

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